Begonia (Begonia semperflorens) showing symptoms of systemic chlorotic ringspots were observed in the central part of Taiwan in May 2006. Infected begonia plants showed faint ringspots in leaves at the early stage of infection. Symptoms turned chlorotic and coalesced as the disease progressed. Electron microscopic examination revealed filamentous virus particles approximately 750 × 13 nm in the crude sap of infected begonia. Typical pinwheel inclusion bodies of potyvirus infection were observed in the ultrathin sections of infected begonia. A virus culture was isolated via mechanical inoculations in Chenopodium quinoa and serologically identified as Zucchini yellow mosaic virus (ZYMV) (1) by ELISA, western blotting, and immunoelectron microscopy. Complementary DNA fragments of viral genomic RNA were cloned, sequenced, and the full-length sequence was submitted to the EMBL database (Accession No. AM422386). The genomic RNA consists of 9,591 nucleotides excluding the poly-A tail and has an identical genome organization to that reported for members of the genus, Potyvirus. The nucleotide sequence of the full-length genome and the deduced amino acid sequence of coat protein share 98% identity to those of ZYMV-CU (Accession No. AJ307036), ZYMV-SG (Accession No. AJ316228), and ZYMV-TW-TN3 (Accession No. AF127929). The virus caused local lesions on the inoculated leaves of C. quinoa, systemic mosaic in cucumber (Cucumis sativus), zucchini (Cucurbita pepo), and Cucumis metuliferus, and chlorotic ringspots in begonia. Symptoms caused by the begonia isolate in cucurbits were much milder than those caused by ZYMVs of cucurbit origin. A ringspot disease with symptoms similar to those caused by ZYMV is also produced on begonia by an Ilarvirus, Prunus necrotic ringspot virus (PNRSV), which was previously identified in begonia (2). To our knowledge, this is the first report of natural infection of ZYMV in begonia.
References: (1) V. Lisa et al. Phytopathology 71:667, 1981. (2) N. Verma et al. Plant Pathol. 51:800, 2002.
